Introduction
To setup the FX3U-232ADP-MB Modbus module, it is necessary to initially configure the serial communication settings. this is relatively straight forward but there is a small issue to take care of when using GX IEC Developer.
Design Considerations
To configure FX3U-232ADP-MB Modbus settings it is necessary to move certain values into a series of special data registers. Logically the 2 examples below are identical but only the first example actually works.
Actual code generated for network 1:
- (MAIN_PRG_LD [PRG])
- (MELSEC code of NVV #1 in MAIN_PRG_LD)
- (* code generated at 02/09/2009 16:51:45, 22 steps, 34 steps for the whole object *)
Example 2 – Using parallel enable branches
- (MAIN_PRG_LD1 [PRG])
- (MELSEC code of NVV #1 in MAIN_PRG_LD1)
- (* code generated at 02/09/2009 16:51:46, 28 steps, 40 steps for the whole object *)
Actual code generated for network 1:
- (MAIN_PRG_LD1 [PRG])
- (MELSEC code of NVV #1 in MAIN_PRG_LD1)
- (* code generated at 02/09/2009 16:51:46, 28 steps, 40 steps for the whole object *)
Summary
As you can see, example 1 creates code with LD instruction followed by several MOV instructions. Example 2 creates LD instructions for every MOV instruction. For successful completion of the Modbus communications setup, example 1 is the only that works.
Further Information
For further information, please refer to the FX3U-232-ADP-MB user manual and GX IEC Developer help files or contact our support desk (support@adroit.co.za).
You can download Tip in PDF format here.